Manganese complexes of salicylaldehyde-alkanolimines as catalysts for the polymerization of 2,6-di-substituted phenols

ABSTRACT

A novel catalyst is disclosed that is useful in the oxidative coupling of phenolic monomers. The catalyst is a manganese chelate that is derived from a salicylaldehyde-alkanolimine.

This is a division of application Ser. No. 880,135 filed Feb. 22, 1978,now U.S. Pat. No. 4,205,007, which in turn is a division of Ser. No.753,506, filed Dec. 21, 1976, now U.S. Pat. No. 4,093,597.

This invention provides a new and novel catalyst that is useful forcatalyzing the oxidative coupling of a phenolic monomer. The catalyst isa manganese chelate that is derived from a salicylaldehyde-alkanolimine.

BACKGROUND OF THE INVENTION

The polyphenylene oxides and methods for their preparation are known inthe art and are described in numerous publications, including Hay U.S.Pat. No. 3,306,874 and U.S. Pat. No. 3,306,875. The Hay processes arebased on the use of copper-amine complex catalysts. Manganese basedcatalysts for the oxidative coupling of phenolic monomers in theformation of polyphenylene oxides are disclosed in McNelis, U.S. Pat.No. 3,220,979; Nakashio, U.S. Pat. No. 3,573,257; Nakashio, U.S. Pat.No. 3,787,361 and Olander, U.S. Pat. No. 3,956,242. In the applicant'scopending applications Ser. No. 491,475 filed July 24, 1974 and Ser. No.534,903 filed Dec. 20, 1974, there are disclosed novel procedures forpolymerizing polyphenylene oxides with complex manganese basedcatalysts. All of these patents and applications are hereby incorporatedby reference.

In U.S. Pat. Nos. 3,444,133 and 3,455,880, there are disclosed manganesechelates of bis-salicylaldehyde ethylene diimine which are reported tobe useful in the preparation of polyphenylene oxides. Japanese printedpatent applications Nos. 26396/73 and 26398/73 also disclose catalystswhich may be manganese or cobalt complexes of one or more compoundsselected from the group consisting of primary amines and aliphatic,alicyclic and aromatic aldehydes. None of these citations disclose amanganese chelate having a salicylaldehyde-alkanolimine component orsuggest its use in the oxidative coupling of phenolic moners under basicconditions.

Accordingly, it is a primary object of this invention to provide a novelmanganese catalyst for the oxidative coupling of phenolic monomers.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a novel catalyst for the oxidativecoupling of phenolic monomers. The novel catalyst is a compound of theformula: ##STR1## wherein R¹ is selected from hydrogen, lower alkyl offrom 1 to 8 carbon atoms and phenyl; halogen, lower alkoxy of from 1 to8 carbon atoms; R² is o-phenylene; lower alkoxy o-phenylene wherein thelower alkoxy group has from 1 to 8 carbon atoms; halo-o-phenylene; loweralkyl-o-phenylene wherein the lower alkyl group has from 1 to 8 carbonatoms; lower alkylene of from 2 to 3 carbon atoms; phenyl lower alkylenewherein the alkylene portion has from 2 to 3 carbon atoms and loweralkyl substituted lower alkylene wherein the lower alkyl group has from1 to 8 carbon atoms and the alkylene portion has from 2 to 3 carbonatoms; R³ is oxygen or nitrogen; R⁴ is lower alkyleneoxy having from 2to 3 carbon atoms, lower alkyl substituted alkyleneoxy wherein the loweralkyl group has from 1 to 8 carbon atoms and the alkylene portion hasfrom 2 to 3 carbon atoms, o-phenyleneoxy, phenyl lower alkyleneoxywherein the alkylene group has from 2 to 3 carbon atoms loweralkyl-o-phenylene wherein the lower alkyl group has from 1 to 8 carbonatoms or phenyl-o-phenyleneoxy; R⁵ is selected from hydrogen, loweralkyl of 1 to 8 carbon atoms or phenyl; and n is 0 or 1.

Included within the scope of Formula I compounds of the formula:##STR2## wherein R¹ is selected from hydrogen, lower alkyl of from 1 to8 carbon atoms and phenyl; and R² is lower alkylene of from 2 to 3carbon atoms or o-phenylene. The preferred species of this formula arethose compounds wherein R¹ is hydrogen and R² is ethylene or o-phenyleneand R⁵ is hydrogen or methyl.

Also included within the scope of Formula I are compounds of theformula: ##STR3## wherein R¹, R² and R⁵ are as hereinabove defined; andR⁶ is lower alkylene of 2 or 3 carbon atoms or o-phenylene.

As used herein and in the appended claims the term lower alkyl of from 1to 8 carbon atoms includes both straight and branched chain hydrocarbongroups such as methyl, ethyl, propyl, hexyl, iso-propyl and the like.The term halogen includes chlorine, bromine, fluorine and iodine. Theterm lower alkoxy includes methoxy, ethoxy, i-propoxy, butoxy, hexoxyand the like. The term lower alkylene of from 2 to 3 carbon atomsincludes groups such as --CH₂ --CH₂ --; --CH₂ --CH₂ --CH₂ ; ##STR4## andthe like. The term phenyl lower alkylene wherein the alkylene portionhas from 2 to 3 carbon atoms includes groups such as ##STR5## and thelike.

The imine component of the novel catalysts of the invention may beprepared by reacting a salicylaldehyde or an appropriate o-hydroxyketone with an alkanolamine according to the following reaction scheme:##STR6## wherein R¹ and R⁵ are the same as hereinabove defined; R⁷ iso-phenylene; lower alkoxy o-phenylene wherein the lower alkoxy group hasfrom 1 to 8 carbon atoms; halo-o-phenylene; lower alkyl o-phenylenewherein the lower alkyl group has from 1 to 8 carbon atoms; loweralkylene of from 2 to 3 carbon atoms; phenyl lower alkylene wherein thealkylene portion has from 2 to 3 carbon atoms; lower alkylene aminelower alkylene wherein the lower alkylene portions have from 2 to 3carbon atoms; o-phenylene amine lower alkylene wherein the loweralkylene portion has from 2 to 3 carbon atoms; and o-phenyleneamino-o-phenylene or substituted derivatives thereof.

Generally the imine may be prepared by heating the salicylaldehydecomponent with the primary alkanolamine in an appropriate solvent suchas benzene or a lower alkanol of 1-6 carbon atoms, i.e. methanol. Ifdesired the manganese salt may be added after the imine is prepared orthe manganese salt, the salicylaldehyde and the primary alkanolamine mayall be combined to form the manganese imine chelate in a single step.

Generally, it is preferred to employ substantially stoichiometricamounts of the chelate forming materials although it may be desirable toutilize an excess of the imine forming components to insuresubstantially complete chelation of the manganese salt.

The suitable manganese salts include the manganese (II) halides such asmanganese (II) chloride (also known as manganous chloride) manganese(II) bromide, manganese (II) iodide, etc., as well as other manganese(II) compounds, such as manganese carbonate, manganese (II) oxalate,manganese (II) sulfate, manganese (II) nitrate, manganese (II)phosphates, etc., including hydrated forms thereof.

The chelate compounds may be formed by reacting substantially equalamounts of the manganese (II) salt and the imine in the presence of asuitable solvent such as a lower alkanol of 1 to 6 carbon atoms such asmethanol. Higher stoichiometries may be employed such as 2 moles ofalkanolamine per mole of manganese.

The imine may be formed from primary aminoalkanols such as ethanolamine;o-aminophenol; 2-(2-aminoethylamine) ethanol; 1-phenyl-2-aminoethanol;1-methyl-2-aminoethanol. Salicylaldehyde per se or its substitutedderivatives may be employed in the formation of the imine.

The process in which the novel manganese based catalyst may be employedto catalyze the oxidative coupling of phenolic monomers may be carriedout by combining the catalyst and monomer in an appropriate organicsolvent in the presence of an oxygen containing gas and alkali.Generally, polymerizations may be carried out by combining the catalystand monomer in an appropriate organic solvent in the presence of anoxygen containing gas. Generally, polymerizations may be carried outusing a mole ratio of phenolic monomer to complexed manganese of from100:1 to 300:1.

The preferred polymerization solvent is a mixture of a lower alkanol of1 to 6 carbon atoms, i.e. methanol and an aromatic organic solvent suchas toluene, benzene, chlorobenzene, xylene or styrene. The preferredreaction composition of a phenolic monomer, i.e., 2,6-xylenol, a loweralkanol, i.e. methanol, and an aromatic organic solvent is from 20:20:60to 16:10:74 weight percent respectively. The exact ratios are notcritical and may be varied depending on the particular catalystemployed.

The catalyst is dissolved in a lower alkanol such as methanol and isadded to the phenolic monomer-organic solvent solution in a reactor thatis equipped with an oxygen inlet tube and an appropriate stirringdevice. In order to increase the stability and reactivity of thecatalyst, primary, secondary or tertiary amines such as n-hexylamine maybe added to the reaction mixture according to the procedure described inU.S. Pat. No. 3,956,242, which is hereby incorporated by reference.Various amines are mentioned in U.S. Pat. No. 3,306,874 and U.S. Pat.No. 3,306,875. The amine may be added at a phenol to amine mole ratiowithin the range of from about 100:0.05 to about 100:15.

The polymerization is initiated by introducing a stream of oxygen at arate that is sufficient to be in excess over that which is absorbed.Alkali is essential and is preferably added as a 50% aqueous solution ofsodium hydroxide sufficient to maintain a mole ratio of 14:1 to 18:1 andmore preferably about 16:1 of phenolic compound to hydroxyl ion duringthe polymerization. Other basic materials are described in U.S. Pat. No.3,956,242. After initiation of the reaction, the temperature does notexceed substantially 45° C., preferably 35° C. When a polyphenyleneoxide having an intrinsic viscosity of about 0.45 dl/g as measured inchloroform at 30° C. is obtained, the reaction may be terminated byadding to the reactor, a sufficient amount of aqueous acetic acid oraqueous sulfuric acid to neutralize the reaction media. Afterneutralization, the entire reaction mixture may be precipitated with asuitable solvent, e.g. methanol, and isolated according to standardtechniques.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following examples illustrate the process of the invention. They aremerely illustrative, and are not to be construed to limit the inventionin any manner whatsoever.

EXAMPLE 1

An imine was formed by condensation of equimolar (0.8196 moles) amountof salicylaldehyde and ethanolamine in about 300 ml of toluene undernitrogen. The mixture was refluxed to remove the theoretical water ofreaction in an apparatus equipped with a Dean-Stark trap. The catalystwas prepared using 41.7 g of this solution containing 3.03 g (0.0184moles) of the imine.

A polymerization reaction was carried out with the following materials:

    ______________________________________                                        toluene    578    ml                                                          methanol   105    ml                                                          2,6-xylenol                                                                              112    g     (16% solids)                                                                              (0.918 moles)                             sodium hydroxide                                                                         4.5    g     (50% sq.)                                             MnCl.sub.2 2.31   g     (0.0184 moles)                                        imine      (41.7 g of toluene solution                                                   containing 3.03 g of the imine                                                prepared hereinabove to give a                                                1:1 complex with manganese)                                        ______________________________________                                    

The 2,6-xylenol, 534 ml of toluene and most of the methanol and all ofthe sodium hydroxide solution were charged into a 1 liter reactorequipped with an oxygen delivery tube and an overhead stirring motor.The catalyst solution comprised of manganese (II) chloride dissolved inmethanol and the toluene solution of the imine formed fromsalicyladehyde and ethanolamine were charged into the reactor and thepolymerization run as a bulk reaction. After 4 hours the reaction isterminated by the addition of aqueous acetic acid. The intrinsicviscosity of the poly (2,6-dimethyl-1,4-phenylene oxide) is 0.21 dl/g asmeasured in chloroform at 30° C.

EXAMPLE 2

The procedure of Example 1 was repeated with the exception that 2.0 g ofn-hexylamine (0.02 mole) is added to the polymerization mixture and thepolymerization was terminated after 4 hours). The intrinsic viscosity ofthe poly (2,6-dimethyl-1,4-phenylene oxide) is 0.50 dl/g as measured inchloroform at 30° C. This clearly demonstrates the rate enhancing effectof ancillary amines.

EXAMPLE 3

A catalyst is prepared in situ by the condensation of 0.799 g ofsalicylaldehyde (0.00656) mole and 0.898 g of 1-phenyl-2-aminoethanol(0.00656 mole) in methanol in the presence of 0.825 g of manganese (II)chloride (0.00656 mole). The catalyst was used directly in thepolymerization described below. The following materials were employed:

    ______________________________________                                        toluene          390    ml                                                    methanol         100    ml                                                    2,6-xylenol      80     g      (0.6557 moles)                                 sodium hydroxide 3.2    g      (50% aq.)                                      n-hexylamine     1.0    g                                                     ______________________________________                                    

The ratio of 2,6-xylenol to manganese was 100:1. A bulk polymerizationwas carried out at 30° C. for 170 minutes at which time the polymer hadan intrinsic viscosity of 0.34 dl/g as measured in chloroform at 30° C.

EXAMPLE 4

An imine was formed by the condensation of 22.35 g of salicylaldehydeand 20 g of o-aminophenol in toluene. The mixture was refluxed and thewater of reaction was collected in a Dean-Stark trap. The imineprecipitated upon cooling. The imine was employed in a 2,6-xylenolpolymerization using the following materials:

    ______________________________________                                        methanol         87.5   ml                                                    chlorobenzene    320    ml                                                    2,6-xylenol      80.0   g      (0.6557 moles)                                 sodium hydroxide 2.4    g      (50% aq.)                                      n-hexylamine     0.8    g      (0.0079 moles)                                 MnCl.sub.2       0.825  g      (0.0065 moles)                                 imine (MW 223)   1.46   g      (0.0065 moles)                                 ______________________________________                                    

A bulk polymerization is carried out for 41 minutes which results in apoly (2,6-dimethyl-1,4-phenylene oxide) having an intrinsic viscosity of0.35 dl/g as measured in chloroform at 30° C.

EXAMPLE 5

An imine was prepared by refluxing 10.0 g of salicylaldehyde and 8.85 gof 2-(2-aminoethylamino) ethanolamine in toluene for minutes. Thereafterthe solvent is stripped off and the yellow product is washed with ether.This imine was employed to prepare poly (2,6-dimethyl-1,4-phenyleneoxide) using the following materials:

    ______________________________________                                        chlorobenzene    393    ml                                                    methanol         90     ml                                                    2,6-xylenol      96     g      (0.786 moles)                                  sodium hydroxide 3.84   g      (50% aq.)                                      n-hexylamine     1.0    g      (0.010 moles)                                  MnCl.sub.2       0.99   g      (0.0078 moles)                                 imine            1.58   g      (0.0078 moles)                                 ______________________________________                                    

A bulk polymerization was carried out for 97 minutes which resulted in apoly (2,6-dimethyl-1,4-phenylene oxide) having an intrinsic viscosity of0.24 dl/g as measured in chloroform at 30° C.

EXAMPLE 6

An imine is prepared by refluxing 2.0 g of 1-phenyl-2-aminoethanol and1.82 g of salicylaldehyde in 100 ml of toluene for several hours. Thereaction solution is diluted to a final volume of 100 ml and useddirectly in a polymerization using the following materials:

    ______________________________________                                        2,6-xylenol       160    g      (1.31 moles)                                  methanol          120    ml                                                   toluene           534    ml                                                   MnCl.sub.2        1.64   g      (0.0131 moles)                                NaOH              8.5    g      (50% aq.)                                     di-methyl-n-butyl amine                                                                         1.32   g      (0.0131 moles)                                imine solution    89     ml                                                   ______________________________________                                    

A polymerization is carried out in a one liter reactor according to thegeneral procedure of Example 5. The manganese chloride in 50 ml ofmethanol is combined with the toluene solution of the imine for 10minutes. The di-methyl-n-butyl amine is added and the mixture is stirredfor 30 minutes. The catalyst solution is added to the polymerizationreactor containing the remaining solvent, base and 2,6-xylenol. Thepolymerization reaction is maintained at 25°-33° C. for 93 minutes, andis quenched with 20 ml of 50% aqueous acetio acid. The isolated poly(2,6-di-methyl-1,4-phenylene oxide) has an intrinsic viscosity of 0.39dl/g as measured in chloroform at 30° C.

Although the above examples have shown various modifications of thepresent invention, other variations are possible in light of the aboveteachings. It is, therefore, to be understood that changes may be madein the particular embodiments of the invention described which arewithin the full intended scope of the invention as defined by theappended claims.

I claim:
 1. A catalyst for the oxidative coupling of a phenolic monomerwhich comprises a compound of the formula: ##STR7## wherein R¹ isselected from hydrogen, lower alkyl of from 1 to 8 carbon atoms andphenyl; halogen, lower alkoxy of from 1 to 8 carbon atoms; R² iso-phenylene; lower alkoxy o-phenylene wherein the lower alkoxy group hasfrom 1 to 8 carbon atoms; halo-o-phenylene; lower alkyl-o-phenylenewherein the lower alkyl group has from 1 to 8 carbon atoms; loweralkylene of from 2 to 3 carbon atoms; phenyl lower alkylene wherein thealkylene portion has from 2 to 3 carbon atoms and lower alkylsubstituted lower alkylene wherein the lower alkyl group has from 1 to 8carbon atoms and the alkylene portion has from 2 to 3 carbon atoms; R³is oxygen or nitrogen; R⁴ is lower alkyleneoxy having from 2 to 3 carbonatoms, lower alkyl substituted alkyleneoxy wherein the lower alkyl grouphas from 1 to 8 carbon atoms and the alkylene portion has from 2 to 3carbon atoms, o-phenyleneoxy, phenyl lower alkyleneoxy wherein thealkylene group has from 2 to 3 carbon atoms lower alkyl-o-phenylenewherein the lower alkyl group has from 1 to 8 carbon atoms orphenyl-o-phenyleneoxy; R⁵ is selected from hydrogen, lower alkyl of 1 to8 carbon atoms or phenyl; and n is 0 or
 1. 2. A catalyst as defined inclaim 1 which comprises a compound of the formula: ##STR8## wherein R¹and R⁵ are selected from hydrogen, lower alkyl of from 1 to 8 carbonatoms and phenyl; and R² is lower alkylene of from 2 to 3 carbon atomsor o-phenylene.
 3. A catalyst as defined in claim 1 which comprises acompound of the formula: ##STR9## wherein R¹ and R⁵ are selected fromhydrogen, lower alkyl of from 1 to 8 carbon atoms and phenyl; and R² andR⁶ are independently lower alkylene of from 2 to 3 carbon atoms oro-phenylene.
 4. A catalyst as defined in claim 3 wherein R¹ and R⁵ arehydrogen and R² and R⁶ are independently lower alkylene of 2 or 3 carbonatoms alkyl substituted lower alkylene of 2 to 3 carbon atoms oro-phenylene.